Publication Date:
2020-01-21
Description:
Salpa thompsoni is an important grazer in the Southern Ocean. It is found from the Subtropical Convergence
southward to the coastal Antarctic Seas but being most abundant in the Antarctic Polar Frontal Zone. Low
temperatures appear to negatively affect their development, limiting their ability to occur in the krill dominated
high Antarctic ecosystems. Yet reports indicate that with ocean warming S. thompsoni have experienced a
southward shift in their distribution. As they are efficient filter feeders, this shift can result in large-scale changes
in the Southern Ocean ecosystem by increasing competitive or predatory interactions with Antarctic krill. To
explore salp bloom dynamics in the Southern Ocean a size-structured S. thompsoni population model was developed
with growth, consumption, reproduction and mortality rates dependent on temperature and chlorophyll
a conditions. The largest uncertainties in S. thompsoni population ecology are individual and population growth
rates, with a recent study identifying the possibility that the life cycle could be much shorter than previously
considered. Here we run a suite of hypothesis scenarios under various environmental conditions to determine the
most appropriate growth rate. Temperature and chlorophyll a were sufficient drivers to recreate seasonal and
interannual dynamics of salp populations at two locations. The most suitable growth model suggests that mean S.
thompsoni growth rates are likely to be ∼1mm body length d−1, 2-fold higher than previous calculations. S.
thompsoni biomass was dependent on bud release time, with larger biomass years corresponding to bud release
occurring during favorable environmental conditions; increasing the survival and growth of blastozooids and
resulting in higher embryo release. This model confirms that it is necessary for growth and reproductive rates to
be flexible in order for the salp population to adapt to varying environmental conditions and provides a framework
that can examine how future salp populations might respond to climate change.
Repository Name:
EPIC Alfred Wegener Institut
Type:
Article
,
peerRev
Format:
application/pdf
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